I also was supposed to receive over 10 BAT for the March payout (according to the estimate it had all month), and instead they processed only ~50% of that (5.346 BAT).
It seems like Brave is trying to save money on payouts by delaying payout to users until the BAT price goes down… but I could be wrong and this could just be a bug. Brave staff needs to confirm what is actually going on!